Method of multiplication of electric signals and its application to radar or like systems

ABSTRACT

Electronic multiplier device for the treatment of two input signals to be multiplied, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously though with opposite signs said periodically reversed signal respectively to one control grid of one tube and to the corresponding control grid of the other tube, means for applying simultaneously though with opposite signs the other of said input signals respectively to the other control grids of said tubes, means for collecting the sum of the anode currents of said tubes, and an alternating current amplifier having its input connected with said last-mentioned means.

United States Patent References Inventor Jacques Maurice Armand Fournier [56] Chatillon-sous-Bagneux, France 'UNTED STATES PATENTS afggi g 2,661,152 12/1953 Elias 235/194 2,741,428 4/1956 Elias.. 235/194 Patented 1971 2 848 161 8/1958 W311 235/194 Assignee Societe Nationale DEtude et de Construction de Moteurs DAviation FOREIGN PATENTS Paris, France 639,928 7/1950 Great Britain 235/194 Priority Apr. 6, 1961 1 790,578 2/ 1 958 Great Britain 235/194 5:35:2 Primary Examiner-T. Hv Tubbesing AttorneyWatson, Cole, Grindle & Watson ABSTRACT: Electronic multiplier device for the treatment of two input signals to be multiplied, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously though with opposite signs METHOD OF MULTIPLICATION OF ELECTRIC SIGNALS AND ITS APPLICATION TO RADAR OR i SYSTEMS, said periodically reversed si nal res ectivel to one control 4 Claims 1 Drawln F g p y g grid of one tube and to the corresponding control grid of the US. Cl 235/ 181, other tube, means for applying simultaneously though with op- 235/194, 328/160, 343/100 CL posite signs the other of said input signals respectively to the Int. Cl G06g 7/19, other control grids of said tubes, means for collecting the sum 606g 7/16 of the anode currents of said tubes, and an alternating current Field of Search 343/ 100.7, amplifier having its input connected with said last-mentioned METHOD OF MULTIPLICATION OF ELECTRIC SIGNALS AND ITS APPLICATION TO RADAR OR LIKE SYSTEMS Multipliers of electric signals capable of operating over a wide range of frequencies generally utilize electronic tubes with two control grids, to which are applied the electric voltages to be multiplied and which will be designated by x and y. The voltage y is multiplied by x in one of the tubes and by x in the other, and the multiplied signals are collected between the anodes of the two tubes.

The process of multiplication is effected as follows:

If the direct current biasing potentials of the grids of the first tube are designated by k and kand g and g'represent those of the grids of the second tube, the following operations are respectively carried out:

By making the difference of the signals (1 42 and (2001- lected on the anodes of the two tubes, there is obtained: kks '+y( g)+ +g')+2xy- Thus, in addition to the desired product 2 xy, we have:

a. Two terms, kk' and gg, which represent the direct currents of the tubes. In order that these terms may cancel each other, it is therefore necessary that kk'=gg',

b. Two terms, y(kg) and x(k'+g). In order that the y term may be zero, it is necessary that k=g. If this condition is fulfilled, there only remains as the result of the operation the desired product xy, to the nearest factor 2 and at term.

ln practice, the conditions k=g and kk=gg'are impossible to obtain precisely, and two filters are necessary to eliminate the terms in x and y. In fact, these conditions are difficult to obtain and to retain in course of time, since they depend on the points of operation of the tubes. Furthermore, in order to obtain a signal of suitable amplitude, it becomes necessary to add a symmetrical direct current amplifier to the multiplier.

The object of the present invention is to obviate these troublesome defects by the use of an expedient which renders inapplicable the strict conditions defined above.

The method in accordance with the present invention consists essentially:

ln effecting the multiplications in each electronic tube in such manner that the result is obtained by the sum of the anode currents of the tube and not by their difference;

In periodically reversing one of the multiplying factors at a predetermined frequency, variable or fixed;

ln amplifying the signal obtained on the anodes of the tubes by an alternating current amplifier and not by direct current.

If it is desired to recover the sign of the multiplied voltage, according to the invention there is then affected a detection synchronous with the said reversal frequency.

A multiplier of this kind can be used with advantage to equip correlation devices. It has a particularly advantageous application for radar installations and in particular for longrange radar and, more generally for all devices transmitting an electromagnetic or other wave and utilizing the echo of the said wave reflected by an obstacle in order to measure the distance to that obstacle.

The description which follows below with reference to the accompanying drawings (given by way of example only and not in any limitative sense) will make it quite clear how the invention may be carried into effect, the special features which are brought out either in the text or in the drawings being understood to form part of the said invention.

The single FIG. is a synoptic diagram of a circuit in accordance with the present invention.

In this circuit, V, and V designate electronic multiplier tubes with two control grids which receive the voltages to be multiplied. As in the case of conventional multipliers, the tubes V, and V, receive respectively the voltages x and x. However, as distinct from these conventional multipliers, these voltages are not always multiplied by y, but by a y signal which is periodically reversed in the two tubes by the action of an inverter 1 combined with an oscillator 0 of variable or fixed frequency. The sum of the voltages delivered by the multiplier tubes V, and V is applied, through the intermediary of a coupling condenser C, to an alternating current amplifier A.

According to the invention, the process of multiplication is effected in the following manner:

Considering the case corresponding to a certain sign of y in each tube, namely +y for V, and -y for V there is obtained in V, by multiplying x by +y:

By making the sum in the common load of the two tubes, there is obtained:

Considering now the period of time for which y is reversed,

there is obtained, in the tube V,:

(k+x) (kxFkk'-ky-l-k'xxy, and in the tube V,:

r '+y)=se'+ y y which gives, when making the addition:

'+s 'y( e)+ '-g)- y On examination of the expression (3and (4it is observed that only the terms 2 xy and 4(k-gchange in sign; only these terms will therefore be amplified by the alternating current amplifier A. A single filter is thus sufficient to eliminate the y term and there will be left only the term 2xy. I

In the particular case where this multiplier is employed in a correlator, the term 4(k-g), which has a mean value of zero by hypothesis since y periodically changes its sign, is thus eliminated in practice by the integrator stage S of the correlafor.

In order to recover the sign of the multiplied voltage, there is carried out at D a detection synchronous with the frequency of reversal.

It will of course be understood that modifications may be made to the form of embodiment which has been described above, in particular by the substitution ofequivalent technical means, without thereby departing from the scope of the present invention.

What I claim is:

1. Electronic multiplier device for the treatment of two input signals to be multiplied, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously thoughwith opposite signs said periodically reversed signal respectively to one control grid of one tube and to the corresponding control grid of the other tube, means for applying simultaneously though with opposite signs the other of said input signals respectively to the other control grids of said tubes, means for collecting the sum of the anode currents of said tubes, and an alternating current amplifier having its input connected with said last-mentioned means.

2. Device as claimed in claim 1, further comprising means for controlling the frequency of the periodic sign reversal of said one of said input signals, and detecting means synchronously associated with said frequency-controlling means and connected with the output of the AC amplifier.

3. Electronic correlating device for the treatment of two input signals to be correlated, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously though with opposite signs said periodically reversed signal respectively to one control grid of one tube and to the corresponding control grid of the other tube, means for applying simultaneously though with opposite signs the other of said input signals respectively to the other control grids of said tubes, means for collecting the sum of the anode currents of said tubes, an alternating current amplifier having its input connected with said last-mentioned means, and an integrator stage connected with the output of said AC amplifier.

4. Device as claimed in claim 3, further comprising means for controlling the frequency of the periodic sign reversal of said one of said input signals, and detecting means 

1. Electronic multiplier device for the treatment of two input signals to be multiplied, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously though with opposite signs said periodically reversed signal respectively to one control grid of one tube and to the corresponding control grid of the other tube, means for applying simultaneously though with opposite signs the other of said input signals respectively to the other control grids of said tubes, means for collecting the sum of the anode currents of said tubes, and an alternating current amplifier having its input connected with said last-mentioned means.
 2. Device as claimed in claim 1, further comprising means for controlling the frequency of the periodic sign reversal of said one of said input signals, and detecting means synchronously associated with said frequency-controlling means and connected with the output of the AC amplifier.
 3. Electronic correlating device for the treatment of two input signals to be correlated, comprising two electronic tubes having each two control grids and an anode, means for periodically reversing the sign of one of said input signals, means for applying simultaneously though with opposite signs said periodically reversed signal respectively to one control grid of one tube and to the corresponding control grid of the other tube, means for applying simultaneously though with opposite signs the other of said input signals respectively to the other control grids of said tubes, means for collecting the sum of the anode currents of said tubes, an alternating current amplifier having its input connected with said last-mentioned means, and an integrator stage connected with the output of said AC amplifier.
 4. Device as claimed in claim 3, further comprising means for controlling the frequency of the periodic sign reversal of said one of said input signals, and detecting means synchronously associated with said frequency-controlling means and positioned intermediate the AC amplifier and the integrator stage. 